June 13: ORD

Today is June 13th. It's the 165th day of the year. 201 days remain. It's week 24 of the year.
 
Unless noted, the following data is based upon observations collected by the National Weather Service, Chicago, at O'Hare International Airport (ORD) between November 1978 and last year. ORD has been the official site of record for Chicago since Thursday, January 17, 1980. Before this, the official site of record was on the south side of Chicago at Midway International Airport (MDW), beginning on Wednesday, July 1, 1942. From Friday, January 1, 1926 through Tuesday, June 30, 1942, the official site was at the University of Chicago. Before that, the official site was at various locations in Chicago going back to Monday, October 16, 1871. Observations taken from October 15, 1870 to October 8, 1871 were lost in the Great Chicago Fire.

According to the National Climatic Data Center (NCDC), the normal high is 79 and the normal low is 57. I've calculated the 33-year averages at 81 and 59.

On the hot side, in 1990 (O'Hare's warmest June 13th) the high was 92 with a low of 71 (O'Hare's warmest low of the date). In 2001 (O'Hare's second warmest June 13th) the high was 91 (our most recent 90s high) with a low of 68. The other hot highs were 94 in 1988 (O'Hare's hottest of the date), 92 in 1987, 91 in 1992 and 91 in 1994. As you can see, five of the six 90s highs occurred between 1987 and 1994. The other warm low was 69 in 1984. The record high of 95 was last set in 1956 at Midway and was originally set at Midway two years earlier in 1954. The record warmest low of 74 occurred back in 1920, at a time when the official readings were taken adjacent to Lake Michigan. 25 of the past 33 highs (76%) were in the: 70s (12) and 80s (13). O'Hare recorded consecutive 70s & 80s highs as follows: eight from 1979 through 1986, six from 1994 through 2000 and six from 2003 through 2008. 20 of the 25 highs in the 70s & 80s (80%) occurred in these three streaks. Six highs (18%) were in the hot 90s and two (6%) were in the cool 60s.

In looking back through the years to the first June at O'Hare in 1959, the following instances were notable: In 1978 the high was 67 with a low of 42, a cool day. In 1969 the high was a cool 64 degrees. In 1968 the high was 76 with a cool low of 43, a 33 degree spread. In 1965 the high was a cool 65 with a low of 46, a cool day. In 1964 the high was a hot 91 degrees. In 1963 the high was 80 with a low of 49, a 31 degree spread. In 1962 the low was a cold 44 degrees. In 1960 the high was a cool 63 with a low of 56, a seven degree spread. In 1959 the high was a cool 67 degrees.

More recently, all the spreads were all large: 36 degrees in 1992 (91/55), 34 degrees in 1995 (85/51), 31 degrees in 1982 (78/47), 31 degrees in 1988 (94/63) and 30 degrees in 1987 (92/62).

On the cool side, in 1985 (tied with 1965 as O'Hare's second coolest June 13th) the high was 71 with the record low of 40, a 31 degree spread. In 2002 the high was 64 (just two degrees above the record coolest high of 62 set way back in 1875) with a low of 55. 29 of the last 33 lows (88%) were in the: 50s (12) and 60s (17). Three lows were in the cool 40s and one was in the warm 70s. O'Hare's coolest June 13th was in 1978 as the high was 67 with a low of 42. Tied with 1985 as the second coolest is 1965 (high of 65, low of 46). O'Hare's coolest high of the date was 63 in 1960.

In regards to last year, 2011: the 45 degree drop in temperature from the high of 95 on 6/8/11 to the low of 50 late 6/9/11 was the greatest two-day drop in temperature since the June record drop of 49 degrees in 1988, 24 years ago. The drop in 1988 was from a high of 103 on June 25 to a low of 54 on June 26. The all-time record, irregardless of month, was a 61 degree drop from 74 degrees to 13 degrees on November 11 and 12, 1911. Data courtesy of The Chicago Weather Center Blog.

The following astronomical data is provided by the United States Naval Observatory. In Crystal Lake, twilight begins at 4:42 and sunrise is at 5:16. Sunset is at 20:31 and twilight ends at 21:05. There's a total of 15 hours, 15 minutes of daylight today and 16 hours, 23 minutes between twilights. We gained a minute of daylight from yesterday. Tomorrow twilight begins at 4:42 and sunrise is at 5:16. The moon is waning crescent, having reached last quarter two days ago at 5:41. Illumination was 33% at midnight, will be 28% at noon and 24% at midnight tonight. Moonrise was at 1:35 this morning. Moonset is at 15:13 this afternoon. Moonrise is at 2:03 tomorrow morning. Moonlight time is 13 hours, 38 minutes which is 34 minutes longer than yesterday. 

Summer began on June 4th and runs for 110 days through September 21st. High temperatures in this period are usually in the 70s and 80s. Highs in the 90s and 100s occur infrequently. Flag Day is tomorrow. Father's Day is in four days.